Notes: Takes place at some vaguely Avenger-y time, and sometime after Hounds of Baskerville. Brief, vague references to Doctor Who. Massive credit to my friend Holly (sleipnirlokison on tumblr) for coming up with the premise and betaing. This was meant to be crack, but then Loki happened and I accidentally angsted all over everything. It gets more fluffy after the first chapter, though. Tell me what you think!

John was slightly alarmed when Sherlock caught his arm halfway up the stairs, halting his progress towards their flat. He was less alarmed by the 'caught his arm' bit, and more by the 'halfway up the stairs' one. Usually, if something was amiss, the consulting detective could tell before they were even out of the cab, let alone through the door.

Sherlock was silent, his eyes narrowed, listening hard. John pricked his own ears. Seeping through the door was an entirely unfamiliar voice, low and threatening.

". . . any idea who I am?"

"Yes, yes," replied Mrs. Hudson breezily, and John winced, feeling Sherlock go rigid beside him. He prayed that whoever was in there wasn't foolish enough to lay a finger on her, for her sake and for that of the unknown intruder. "You're one of Sherlock's clients. Don't worry; he gets all sorts. Eat your biscuits, dear."

Sherlock removed his hand from John's arm and began to creep – no, to prowl up the stairs. John followed him while Mrs. Hudson continued to fuss over the intruder.

"Honestly, the state of you! Worse than Sherlock. Though he hasn't been so bad these days, what with that doctor of his looking after him . . ."

"Yes, thank you, Mrs. Hudson," said Sherlock firmly as he pushed the door open.

A man was sitting in Sherlock's customary chair, clad in an expensive black suit and green scarf despite the warm weather. Mrs. Hudson hadn't been exaggerating when she said that he was worse than Sherlock. His skin was sallow and pale, contrasting sharply with his dark, greasy hair. Even through his layers of fabric it was obvious that he was unhealthily thin; best guess, John would say that he was naturally slim to begin with and made slimmer by neglect and stress. The circles under his eyes attested to that.

He had been frowning at a Jammy Dodger when they entered, but swept to his feet with effortless poise an instant later. His eyes nearly matched Sherlock's in color and definitely matched them in intensity.

"Sherlock Holmes," the stranger greeted. He did not extend his hand. "I have heard such . . . fascinating stories about you."

"I rather suspect I've heard some about you, as well," Sherlock returned. John wondered absently how two people who were approximately the same height could both look down their noses at each other. "Loki."

The stranger smiled a shark's smile as the air around him began to shimmer. John gaped in disbelief and Mrs. Hudson gave a startled squeak as the man's outfit shifted before their eyes. Wait – had Sherlock said Loki?

"You are certainly more clever than most humans," the man – god? No, no, absolutely not – said. His attire had solidified into some cross between a medieval tunic and a leather jacket, all black and gold and green. "Unless, of course, you simply recognize my face from your elder brother's pilfered records . . ."

"I have better things to do with my time than to steal from my brother," said Sherlock.

Despite the situation, John found he still had enough of his composure intact to roll his eyes at this blatant falsehood.

"It's not exactly a difficult deduction," Sherlock continued. "Your earlier question to Mrs. Hudson suggests that you have a very high opinion of your own status; I'd say delusions of grandeur, but your manner speaks of a sort of breeding which is difficult to fake. Not just nobility, but royalty. Not delusions, then, but not entirely accurate, either."

"Sherlock," said John warningly, seeing the cold imitation of mirth slip from the – the god's face. Sherlock ignored him.

"You're clearly unwell; underfed and overstressed. The extent of your malnutrition is beyond mere absentmindedness; it is almost certainly the result of starvation, self-inflicted or otherwise. Your body language speaks of psychological trauma which could only be produced by repeated physical abuse over an extended period of time."

"Sherlock," said John, more sharply. Loki was trembling slightly, eyes wide, and – oh god, were those tears? Yes. He was crying. Sherlock was making a Norse god cry. Of course he was. Christ.

"That sort of treatment would never have been allowed if you still belonged to the class which you ascribe to yourself; exiled, then. Any exiled royalty on Earth I'd know about it, so obviously you are of extraterrestrial origin. You're too defensive for a king, which makes you a prince, which means that some older member of your family must still be alive, and yet you can't or won't go to them for help. Additionally, you were startled and confused by Mrs. Hudson's care, as if you're not accustomed to anyone looking towards your wellbeing. You aren't just estranged from your family; you were an outcast from the very beginning.

"Conclusion: you are an exiled alien prince with a vested interest in Earth, despised by your people and rejected by your family –"

"Sherlock!"

Sherlock finally closed his mouth, looking at John with some mixture of bemusement and offense.

"What?"

That was when the ball of blue light hit him.